Information on how to install and use NTFS-3G for Mac OS X can be found in the User Guide.

Known issues:

Files with filenames created in Windows containing international characters with accents, umlauts and similar dots and lines, or filenames with korean characters might seem unreadable in the Finder. This is because Finder apparently expects all filenames to appear in unicode decomposed form, while NTFS allows both composed and decomposed form filenames. This issue is hard to solve in a pretty way, but you should still be able to access these files when using the Terminal. For me, copying the affected files to a HFS+ drive using the command "cp" worked fine.

After installing ntfs-3g, all NTFS drives will disappear from the "Startup Disk" preference pane. Disabling or uninstalling ntfs-3g brings them back. I don't have a solution for this, but you can still choose your startup drive by:

Holding down the Option key during boot (or Alt for non-Apple keyboards).